The efficacy of enzymes used as therapeutic agents (e.g., E. coli L-asparaginase and lysosomal hydrolases) might be improved by any or all of the following: directed uptake by target tissues; prolonged clearance time; reduced antigenicity; and increased resistance to destruction by proteases. Direct modification of proteins by glycosylation offers one promising route to achieve these objectives, and incorporation into liposomes, which are also modified by the attachment of oligosaccharides, offers another. We have established a mild and convenient procedure for protein modification by glycosylation, and have shown that the attachment of different oligosaccharides affects the clearance of E. coli asparaginase in mice in different ways. Our objectives now are to extend these procedures to allow glycosylation with more complex oligosaccharides; to study the effects of such modification on various properties of the modified proteins, including clearance time following injection into mice, biological activity, anti-tumor activity, stability towards protease digestion, and anti-genicity. In the case of E. coli asparaginase, an added long-term objective of modification is to improve anti-tumor activity, either by extending clearance time, by causing the enzyme to be taken up selectively by tumor cells, or both. Modification is achieved by reductive coupling with sodium cyanoborohydride; clearance is followed by direct assay for asparaginase in samples drawn from the tail veins of mice. Other analytical procedures are described in the proposal, together with descriptions of experiments involving coupling of complex oligosaccharides; experiments to assess the feasibility of using glycosyl transferases to attach additional sugars to oligosaccharide "primers".